A gene to help the butterfly's disguise

A Heliconius erato erato female displays its warning coloration while gathering Cephaelis tomentosa pollen. The wing patterns of these butterflies serve as "stop signs" for would-be predators, delivering the message "Don't eat me, I taste bad." In this issue Reed et al. determine that the homebox gene optix drives the evolution of red warning coloration across the genus Heliconius. Therefore allowing these butterflies to participate in numerous color pattern mimicry complexes throughout the neotropics.
[Chris Jiggins]

Heliconius butterflies include more than 40 different species of butterfly, and they are famous for their strikingly unique and colorful wing patterns. They have evolved their current wing colors by mimicking, or copying, the warning signals of other species of butterfly.

Now, researchers say that a single gene, called optix, is responsible for the patterns of red coloration seen on the butterflies' wings. Robert Reed and colleagues used a combination of genetic mapping techniques, gene expression methods and population studies to discover that optix controls the patterns of red coloration on a number of Heliconius species.

This optix gene has previously been associated with the butterfly visual system, so Reed and his team suggest that the gene was adopted for red color patterns after being used for a different, ancestral function long ago.

Their study demonstrates that genes related to evolution can still be identified in non-model systems, like Heliconius butterflies, by using a combination of developmental genetics and population biology.